1. Field of the Invention
The present invention relates generally to a slice level corrector, and more specifically to a slice level corrector for an optical recording/reproducing system. The voltage level of a slice signal is corrected such that it is not influenced by noise when an information signal, which is read out of a recording medium, is detected as a series of binary-coded signals.
2. Description of the Prior Art
In optical systems for recording and reproducing digital information by irradiating a light beam on a disc type recording medium, for example, by using an optical pickup, both self-clock enabling frequency modulation (FM) systems and modified frequency modulation (MFM) systems have often been used. Recently, however, MFM systems have often been used because the systems can record data at a high density which is twice as great as in FM systems.
In the MFM system, however, an RC circuit is included in an information data reading circuit to eliminate the dc component from the information data signal read out of an optical disc with an optical pickup. The read information signal is superimposed upon a damping dc component and thus a series of binary-coded signals having different duty factors are detected. There is a problem however, in that error information may be detected. Further, the positive voltage level of the information signal does not match the negative voltage level thereof on the time base, so that there exists another problem in that different duty factors are produced due to the offset in the dc level. This causes an error in the information signal. Furthermore, when noise is superimposed upon the waveform when an information signal is absent, a false signal is generated which is mixed with the data signal.